The present invention relates to a door check designed to close automatically an open door. The door check may be applied to various units such as house doors, kitchen closures, entrance/exist doors or baggage space closures of aircrafts, buses or any other vehicles.
Most of conventional closers which have heretofore been put into practical use are of the oil cylinder type in which a piston is slidably received in a cylinder accommodating a spring and the oil. When the door is opened, the spring is deformed to store energy, whereas, when the door is closed, a damper effect is applied to the closing door by the use of the fluid resistance of the oil.
There has also been proposed a mechanical door check in which, when the door is opened, a spring is deformed to store energy, and when the door is closed, the force released from the spring is transmitted to a mechanical, centrifugal governor or an electromagnetic governor after the speed thereof has been increased through a speed increasing gear train to thereby apply a damper effect to the closing door (see, for example, Japanese Patent Publication No. 52-21810 (1977)).
Further, Japanese Patent Publication No. 52-3227 (1977) discloses a friction brake type door check.
The oil cylinder type door check has the problem that the damper effect varies with the change in room temperature because this type of door check utilizes the fluid resistance of the oil sealed in the cylinder to obtain a damper effect. More specifically, when the temperature rises, the viscosity of the oil lowers, so that the fluid resistance lowers and the door closing speed therefore increases, whereas, when the temperature lowers, the fluid resistance of the oil rises and therefore the door closing speed lowers. For this reason, it is necessary in the case of the conventional oil cylinder type door check to adjust the door closing speed. The oil cylinder type door check also suffers from the disadvantage that the sealed oil may leak, which means that this type of door check is inferior from the viewpoint of durability. Further, since it is necessary to prepare a casing including a cylinder which is able to endure large spring force and high oil pressure, the size and weight of the door check itself increase unavoidably. If the door check is heavy, the mounting operation becomes troublesome.
The mechanical door check is free from the above-described problems, that is, variations in the damper effect with the change in temperature and the leakage of the oil, but it has the problem that the overall size is disadvantageously large because it is necessary in order to obtain a predetermined speed increase ratio to dispose a large number of gears between the spring and the governor. If the speed increasing gear train is formed using spur gears, the gear train becomes long and the inertia of the gear train when rotated increases, so that, when the door is opened and closed, the gear train does not start rotating smoothly. Thus, this type of door check suffers from inferior operability (feeling) in opening and closing the door.
Regardless of the type, door checks are demanded not only to have functional characteristics that it is possible to open the door with light force and with good feeling, not to mention that it is possible to close the door reliably, but also to have an external appearance which does not damage the appearance of the door and the surroundings.